1. Technical Field of the Invention
The present invention relates generally to utility networks and more particularly to load control management in such utility networks.
2. Related Art
Utility networks have been known for many years to service a great variety of electrical loads. In such utility networks, large generating units generate large quantities of electrical energy. This electrical energy is coupled to high voltage transmission lines. Transmission lines interconnect with one other and transmit the electrical energy at high voltages about a service area. Each of the transmission lines is independent switchable and protected via circuit breakers. The transmission lines often interconnect at substations. These substations include transformers that transform the electrical voltage (which is typically at 60 hertz in the United States) from transmission voltages ranging from 500 kilovolts down to 69 kilovolts to a distribution voltage, typically ranging between 25 kilovolts and 1.5 kilovolts.
Electrical loads are typically serviced at distribution voltage levels. While some loads are serviced immediately adjacent substations, e.g., industrial loads, most loads are serviced via distribution lines at the distribution voltage level. In such cases, a single distribution transformer located in the substation services a large number of individual electrical loads. These electrical loads include businesses, e.g., office buildings, shops, etc., as well as residential customers. In serving these loads, additional transformers may be located adjacent a particular load(s) to further reduce the voltage to 240 volts, 480 volts or other distribution voltage level.
As utility networks have grown over the last one hundred years, generating plants have been progressively constructed to be larger. Modern power plants now produce as much as 600 to 900 megawatts per generating unit. Thus, each generating unit serves a huge number of electrical loads. With large generator units, significant efficiencies are obtained that reduce the cost of generating each kilowatt. However, because each individual generating unit is so large, the loss of any particular generator causes significant problems in the operation of the utility network. Thus, steps are taken to ensure that sufficient generating plants are online at any given time to serve the utility network""s load should one or more generating units go unexpectedly off-line.
Because electrical load serviced by utility network varies by time of day, day of week, week of month, and month of year, the generating capacity that is on-line at any given time is dynamically managed to ensure that enough generation is online to service expected loading levels for the particular time. Historically, demand for electrical energy reaches its peak either in the hottest days of the summer time or alternatively in the coldest days of the winter. Further, loading is typically larger during working days than it is on weekends. Scheduled maintenance of the generating units is typically performed corresponding to lower loading periods. However, unplanned outages of generating units will oftentimes cause significant problems in servicing electrical loads.
Deregulation of electrical utilities has been occurring over the past number of years. Such deregulation has in many cases segregated the ownership of electrical generating plants from transmission networks. Further, electrical generation has been treated somewhat as a commodity that is available to the highest bidder. The West Coast in particular has seen problems caused in part by such deregulation. Deregulation as well as increased environmental awareness of the effects of generating plants has made the construction of additional generation capacity slower than it previously has been. However, the growth of load, which is the demand placed upon generating capacity has increased with population in business usage. Thus, recently, during some loading periods, insufficient generation capacity has been available to service the loading requirements of the utility networks. Having sufficient electrical generation online to service online load is an absolute requirement for maintaining the Operation of the utility network (in order to maintain the frequency of the system, to avoid voltage collapse, to avoid overloading of generating plants, etc.), the only alternative available for utility companies in such conditions is to indiscriminately disconnect electrical loads from their transmission and/or distribution networks. Such operations are wholly unacceptable.
While steps are being taken to increase generating capacity to service existing expected load, problems that caused a shortfall to exist in the first place have not been overcome. Thus, further shortages are expected to occur. When these further shortages occur, load shedding will be continue to be employed to ensure that the load does not exceed the generating capacity of particular utility networks. Unfortunately, as load continues to increase, if transmission and distribution lines are not newly constructed to meet such new load, even if sufficient generating capacity exists, the loads still cannot be serviced. Load shedding will be required for these reasons as well.
An alternative to indiscriminate load shedding is selective load shedding. Utility networks typically enter into agreements with large industrial users that allow the utilities to reduced or disrupt electrical service to these customers. As compensation for allowing the utility company to reduce/cease its service when required, these customers receive a reduced rate for such electrical service. However, the utility company cannot interrupt most loads. For example, manufacturing facilities having assembly lines, industrial processes, and other operations would be harmed greatly by the disruption of electrical power. The utility customers therefore cannot enter into service interruption agreements with these companies. Thus, the avenue of interruptible industrial load is not one that may be used to greatly decrease electrical load during high loading periods.
Some utility companies have attempted to manage electrical load by controlling particular appliances within a plurality of homes or small businesses. One example of such programs is to place a switch on water heaters within homes and businesses, the switch being operable via a radio frequency carrier. Upon operation of these switches via the radio frequency carrier, a plurality of water heaters will be removed from service to reduce the loading on the electrical utility. However, the cost of installing and operating such load management equipment is high. Further, the particular customer may easily alter these devices so that they are inoperable. Thus, these devices have failed to produce any significant benefits in reducing load on utility network.
Thus, there exists a need in the art for a system and method of operation that will provide load management within a utility network that overcomes these shortcomings, among others.
Thus, in order to overcome the above-described shortcomings among others, a load management system of the present invention includes a load management control center, at least one power management termination system, a plurality of power line nodes, and a plurality of load management devices.
This system is operable so that the load management control center may independently, or as a group, control each of the load management devices.
According to one aspect of the present invention, the load management control center accesses the load management devices across a communication network that includes a power line network. This powerline network uses as a media the power lines that also carry the 60 hertz electrical power to a serviced load. Using this power line carrier local area network, the load management control center may query a plurality of the load management devices. In querying the load management devices, the load management control center may determine the particular load level that is being serviced by each of the load management devices and that may be terminated or interrupted by the load management devices. These load management devices may control electrical service to all of a particular home, a particular business, or another type of structure receiving electrical service. Further, these load management devices may control the electrical power to one or more of a plurality of appliances located within such homes or businesses. Thus, the load management control center may individually or as a group direct the load management devices to drop their corresponding loads.
Each load management devices may have a unique address so that the load management control center may individually address the load management device. A subscriber may therefore register the load management device so that the load management device is related to the identity of a particular subscriber within the corresponding utility network. In such case, the particular subscriber may receive reduced electrical utility rates in return for allowing all or a portion of subscriber""s corresponding electrical load to be interrupted by the utility company.
According to another aspect of the present invention, the load management devices are addressed as a group or set of groups by the load management control center during load shedding operations. In such case, when a rapid reduction in an electrical load is required, the load manager control center initiate load reduction at a desired level via the issuance of a single broadcast command. This type of load shedding is achievable within a time frame that is satisfactory to compensate for the loss of a generating plant.
The system and method of the present invention also provides a great many other options for controlling loads within a utility network. Because the loads are individually controllable using the system and method of the present invention, subscribers may disrupt or enable loads within their home or business via interaction with the load management control center. This interaction may be had across the Internet or another communication system. Thus, if the subscriber will be away from his home for a period of time he may selectively disable the utility service and may also selectively enable the utility service without physical access of the home.
These advantages will become apparent through a reading of the detailed description of the figures that follow.